This invention relates to intraluninal grafts for repairing defects in arteries and other lumens within the body. More particularly, the present invention relates to a bifurcated graft that is supported by a stent lattice and has legs that are independently flexible.
An abdominal aortic aneurysm is a sac caused by an abnormal dilation of the wall of the aorta as it passes through the abdomen. The aorta is the main artery of the body, supplying blood to various organs and parts of the body. It arises from the left ventricle of the heart, passes upward, bends over and passes down through the thorax and through the abdomen, and finally divides into the two iliac arteries which supply blood to the pelvis and lower extremities. The aneurysm ordinarily occurs in the portion of the aorta below the kidneys. When left untreated, the aneurysm will eventually cause the sac to rupture with ensuing fatal hemorrhaging in a very short time. The repair of abdominal aortic aneurysms has typically required major abdominal surgery in which the diseased and aneurysmal segment of the aorta is removed and replaced with a prosthetic device, such as a synthetic graft.
As with all major surgeries, there are many disadvantages to the foregoing surgical technique, the foremost of which is the high mortality and morbidity rate associated with surgical intervention of this magnitude. Other disadvantages of conventional surgical repair include the extensive recovery period associated with such surgery; difficulties in suturing the graft to the aorta; the loss of the existing thrombosis to support and reinforce the graft; the unsuitability of the surgery for many patients, particularly older patients exhibiting co-morbid conditions; and the problems associated with performing the surgical procedure on an emergency basis after the aneurysm has already ruptured.
In view of the foregoing disadvantages of conventional surgical repair techniques, techniques have been developed for repairing abdominal aortic aneurysms by intraluminally delivering an aortic graft to the aneurysm site through the use of a catheter based delivery system, and securing the graft within the aorta using an expandable stent. Since the first documented clinical application of this technique was reported, the technique has gained more widespread recognition and is being used more commonly. As vascular surgeons have become more experienced with this endovascular technique, however, certain problems have been encountered.
One of the biggest problems has been the kinking and/or twisting of the graft both during and after the graft has been implanted due to the often extreme tortuosity of the vessels adjacent to the aneurysm. A flexible stent-graft is required to accommodate the various bends in the vessels without kinking or twisting.
Endovascular repair of the abdominal aortic aneurysm (AAA) using a stent/graft prosthesis that is assembled in-situ is gaining acceptance due, in part, to the added flexibility that can be gained by providing limb portions that are not attached to the trunk portion. However, such modular stent-grafts can embody several disadvantages. There can be an increased risk of leakage in the area of the trunk portion where the limb portions are attached due to an inadequate seal between the limb portion and trunk portion or by the bending of the limb portion as it conforms to the patient""s vasculature. Additionally, there can be a lack of support in the area of the bifurcation.
Therefore, there exists a need for an unibody or a modular bifurcated graft which provides a trunk portion having sufficient flexibility and support in the area of the bifurcation to allow the limb portions to bend in conformance to the patient""s vasculature without the associated risk of leakage. The present invention addresses these and other needs.
Briefly and in general terms, the present invention is embodied in a bifurcated graft having a trunk portion with a flexible bifurcation that allows the leg portions to flex independently. Aspects of the present invention are applicable to both unibody and modular graft devices. In modular graft devices, the flexible bifurcation facilitates the attachment of limb portions which bend to conform to the patient""s vasculature.
In one aspect of the invention, a flexible bifurcation is produced by combining a flexible Nitinol stent lattice with a woven bifurcated graft The flexible bifurcation allows each leg to bend in a wide and independent range of motion both in and out of the plane of the trunk.
In another aspect of the invention, a stent lattice is provided which is continuous throughout the trunk portion and extends into each leg. Since the stent lattice is continuous, additional support is provided in the area of the bifurcation. Furthermore, the presence of the stent lattice in each leg provides additional support for the limb portions and inhibits substantial kinking of the graft material when the limb portions bend upon being positioned within branch vessels. Moreover, the stent lattice provides column support for the graft to resist migration and help prevent drifting of the top of the graft during deployment.
The stent lattice may extend partially or completely around the circumference of each leg. Additional support rings, either partial of full, may be provided at the distal end of each leg in order to more securely attach a limb portion to the trunk portion.
Other features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.